Publications
80 results found
Cinosi N, Walker SP, Bluck M, et al., 2014, CFD ANALYSIS OF THE FLOW IN CRUD-COATED NUCLEAR ROD BUNDLES, 22nd International Conference on Nuclear Engineering (ICONE22), Publisher: AMER SOC MECHANICAL ENGINEERS
Bluck M, Cinosi N, Walker S, 2013, A multilevel hierarchical preconditioner technique for multiscale and complex em scattering bodies, Pages: 1519-1522
This paper considers the solution of the combined field integral equation (CFIE) for lossy/dielectric problems. Hierarchical conforming bases are developed which are subsequently used in the construction of a multilevel Schwarz type preconditioner. The effectiveness of this approach is demonstrated by the computation of scattering in free space from a range of spheres with different permittivity (non PEC material). The resulting schemes are shown to be faster than conventional schemes. © 2013 IEEE.
Bluck MJ, Cinosi NN, Walker SP, 2013, A p-MUS preconditioner for the EFIE, IEEE Transactions on Antennas and Propagation, Vol: n/a, ISSN: 0018-926X
This paper considers the solution of the electric field integral equation (EFIE) in electromagnetics. As with associated finite element methods, their solution relies upon the construction of conforming bases. Whilst lowest order (RWG) spaces are near ubiquitous, their extension to higher order offers, potentially, a number of benefits in terms of accuracy and efficiency, which has been well documented in both finite elements and integral equation formulations. A further evolution of higher order conforming bases is the hierarchical basis. These have demonstrated considerable gains in efficiency in finite element applications. Such bases allow for the development of effective acceleration schemes, for instance, the multilevel Schwarz type preconditioner (p-MUS). An obvious question arises as to the applicability of such hierarchical bases and their associated acceleration schemes to integral equations. It is seen that the conclusions as to their efficacy depend strongly on the scattering regime. In particular, high frequency problems (those where the wavelength is the principal determinant of mesh size) are shown to benefit little from hierarchical functions. On the other hand, for {\lq low frequency\rq} problems (where geometry is the main determinant of mesh size), there are significant improvements in performance over corresponding interpolatory schemes.
Bluck MJ, Cinosi N, Walker SP, 2013, A multilevel hierarchical preconditioner for multiscale EM scattering
Integral equation schemes, both EFIE and MFIE, have become a powerful tool, particularly with the development of accelerated schemes such as the fast multipole method (FMM). Key to most such treatments is the requirement to solve matrix equations iteratively, which at their core involve matrixvector multiplications. Much of the cost of such solutions then depends on the number of iterations and the cost per iteration. The vast majority of integral equations implementations employ the simplest Rao-WiltonGlisson (RWG) basis functions on triangles. High order interpolatory bases have been developed which (in principle) offer improved accuracy for a given cost. Within the current developments, the next natural step beyond high order interpolatory methods is to arrange these bases hierarchically, as already experienced within the finite element community. Of themselves hierarchical bases offer little more than their high order interpolatory counterparts. However, as has been demonstrated in finite elements it is possible to employ this hierarchical structure to great effect in the reduction of the computational cost of the underlying iterative scheme via a multilevel Schwarz type preconditioner. In this paper we attempt to apply such hierarchical bases and their associated acceleration schemes to integral equations. The results suggest that their efficacy depend strongly on the scattering regime. In particular, high frequency problems (those where the wavelength is the principal determinant of mesh size) are shown to benefit little from hierarchical functions. Unlike their finite element counterparts, equivalent p-MUS integral equation schemes appear to offer little gain, if any, over nonhierarchical schemes. On the other hand, for ̀low frequency' problems, such as scattering of objects with sub-wavelength features (where geometry is the main determinant of mesh size), there are significant improvements in performance over corresponding interpolatory schemes. Copyright &
Bluck MJ, 2012, Conforming Hierarchical Basis Functions, Communications in Computational Physics, Vol: 12, Pages: 1215-1256, ISSN: 1815-2406
A unified process for the construction of hierarchical conforming bases on a range of element types is proposed based on an ab initio preservation of the under- lying cohomology. This process supports not only the most common simplicial ele- ment types, as are now well known, but is generalized to squares, hexahedra, prisms and importantly pyramids. Whilst these latter cases have received (to varying de- grees) attention in the literature, their foundation is less well developed than for the simplicial case. The generalization discussed in this paper is effected by recourse to basic ideas from algebraic topology (differential forms, homology, cohomology, etc) and as such extends the fundamental theoretical framework established by the work of Hiptmair [16–18] and Arnold et al. [4] for simplices. The process of forming hierar- chical bases involves a recursive orthogonalization and it is shown that the resulting finite element mass, quasi-stiffness and composite matrices exhibit exponential or bet- ter growth in condition number.
Cinosi N, Bluck M, Walker S, 2012, Application of Time-Domain BIE to sub-wavelength Scattering Bodies with Finite Conductivity, International Conference on Electromagnetics in Advanced Applications (ICEAA) / IEEE-APS Topical Conference on Antennas and Propagation in Wireless Communications (IEEE APWC) / URSI Electromagnetic Environment and Interference Symposium (EEIS), Publisher: IEEE, Pages: 1177-1179
Cinosi N, Walker S, Bluck M, 2011, Time-domain bie analysis of large electromagnetic scattering problems with Impedance Boundary Condition, Pages: 1172-1175
Methods for solving the electromagnetic scattering of computationally large problems in a fast and efficient way are well established. However their application is limited to PEC scattering bodies, whilst when applied to lossy or conducting materials they become inefficient and less desirable. In this paper we extend the capabilities of these fast methods to solve for non-dispersive conductors by using the approximation of the Impedance Boundary Condition. © 2011 IEEE.
Bluck M, Cinosi N, Walker S, 2011, A multilevel hierarchical preconditioner for the electric field integral equation, Pages: 1180-1183
This paper considers the solution of the electric field integral equation (EFIE). Hierarchical conforming bases are developed which are subsequently used in the construction of a multilevel Schwarz type preconditioner. The effectiveness of this approach is demonstrated by the computation of scattering from a range of perfectly conducting objects including spheres, cubes, plates and dihedrals. The resulting schemes are shown to be faster than conventional schemes by approximately an order of magnitude. © 2011 IEEE.
Cinosi N, Haq I, Bluck M, et al., 2011, The effective thermal conductivity of crud and heat transfer from crud-coated PWR fuel, Nuclear Engineering and Design: an international journal devoted to the thermal, mechanical, materials, and structural aspects of nuclear fission energy, Vol: 241, Pages: 792-798, ISSN: 0029-5493
Water-filled crud on the surface of PWR fuel could offer resistance to the flow of heat, which might be expected to cause higher clad temperatures, and probably more fuel failures, than are actually observed. However, there is some evidence from post-irradiation inspection that the crud is penetrated by pores large enough to permit vapour formation, and it is believed these provide a mechanism for `wick boiling' to occur, which modifies, and indeed can under some circumstances actually improve, heat transfer. This phenomenon is investigated using a two-dimensional coupled multi-physics model, accounting for the flow of water, heat and dissolved species within the crud. The fuel thermal performance is characterized in terms of an effective crud thermal conductivity derived from the use of this model, and the non-linear dependence this effective thermal conductivity has on parameters such as crud thickness and pore density is determined.
D'Arcy M, Weiss DJ, Bluck M, et al., 2011, Adsorption kinetics, capacity and mechanism of arsenate and phosphate on a bifunctional TiO2-Fe2O3 bi-composite, Journal of Colloid and Interface Science, Vol: 364, Pages: 205-212
Haq I, Cinosi N, Bluck MJ, et al., 2011, Modelling heat transfer and dissolved species concentrations within PWR crud, Nuclear Engineering and Design: an international journal devoted to the thermal, mechanical, materials, and structural aspects of nuclear fission energy
The crud formed on PWR fuel tends to contain "chimneys" penetrating down to the metal surface. This provides an opportunity for wick-boiling to occur. This is associated with the generation of very high concentrations (many tens of times the bulk values) of dissolved species within the crud, and associated significant increase in the local saturation temperature. These both have consequences for cladding corrosion, and the accumulation of boron in the crud contributes to the phenomenon termed "axial offset anomaly". We present here detailed, coupled two-dimensional models of these processes, which allow the three linked phenomena, heat conduction, advection and diffusion of species in the water, and diffusion of the water itself, to be modeled and their aggregate effect to be seen. (C) 2010 Elsevier B.V. All rights reserved.
Ahmad M, Alexandrou I, Al-Nuaimy W, et al., 2010, WCE 2010 - World Congress on Engineering 2010: Preface, WCE 2010 - World Congress on Engineering 2010, Vol: 2
Cinosi N, Walker SP, Bluck MJ, 2009, Integral equation transient analysis of experiments on electromagnetic scattering from sub-wavelength apertures, International Conference on Electromagnetics in Advanced Applications (ICEAA 2009), Publisher: IEEE, Pages: 537-540
Cinosi N, Walker SP, Refig A, et al., 2007, Integral equation time domain analysis of frequency-dependent transmission through aperture arrays, Pages: 960-963
Whereas a single sub-wavelength aperture transmits little light, much greater transmission is observed through an array of such apertures. Plainly the apertures interact, at a length scale related to their spacing, and encourage the transmission of the light through the small holes. This behaviour is studied via solution of the governing Maxwell equations in the space surrounding the perforated plate, and the field distributions associated with this anomalous transmission are investigated. © 2007 IEEE.
Bluck MJ, Walker SP, 2007, Polynomial basis functions on pyramidal elements, Communications in Numerical Methods in Engineering
Bluck M J, Walker S P, 2007, High-Order Discrete Helmholtz Decompositions for the Electric Field Integral Equation, IEEE Transactions on Antennas and Propagation, Vol: 55, Pages: 1338-1347, ISSN: 0018-926X
Cinosi N, Walker SP, Bluck MJ, 2007, Transient near field analysis of optical modes in sub-wavelength arrays, Workshop on Computational Electromagnetics in Time-Domain, Publisher: IEEE, Pages: 104-107
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Bluck MJ, Hatzipetros A, Walker SP, 2006, Applications of differential forms to boundary integral equations, Antennas and Propagation, IEEE Transactions on, Vol: 54, Pages: 1781-1796, ISSN: 0018-926X
Bluck MJ, Hatzipetros A, Walker SP, 2006, Applications of differential forms to boundary integral equations, Antennas and Propagation, IEEE Transactions on, Vol: 54, Pages: 1781-1796, ISSN: 0018-926X
Bluck MJ, Walker SP, 2005, Algebraic topology and computational electromagnetics, Pages: 853-856
In this paper we discuss the application of algebraic topology to computational electromagnetics. Basic homology and cohomology theory is explained in the context of numerical schemes. We will show how these concepts influence the choice of discrete spaces for both finite and boundary element methods. Spaces on simplicial manifolds (triangles, tetrahedra), cartesian product manifolds (quadrilaterals, hexahedra) and prismatic manifolds are easily constructed in the light of these topological considerations. In particular, Nedelec, Raviart-Thomas, Whitney and Rao-Wilton-Glisson type function spaces are easily obtained as special cases. This approach is not restricted to affine manifolds with results being equally valid for the general curvilinear case. In general an adjoint form of the commuting de Rham diagram is shown to hold and how this property affect convergence is discussed.
Cinosi N, Walker SP, Bluck MJ, 2004, Modelling of sub-wavelength optical apertures in thin metal sheets via 3D transient Maxwell's equations, New York, 5th international conference on numerical simulation of optoelectronic devices, 19 - 22 September 2005, Berlin, GERMANY, Publisher: Ieee, Pages: 99-100
Cinosi N, Walker SP, Bluck MJ, 2004, Modelling of sub-wavelength optical apertures in thin metal sheets via 3D transient Maxwell's equations, New York, 5th international conference on numerical simulation of optoelectronic devices, 19 - 22 September 2005, Berlin, GERMANY, Publisher: Ieee, Pages: 99-100
Bluck MJ, Walker SP, 2003, Cohomology and the construction of discrete function spaces for finite and boundary element methods, Pages: 99-102
In this paper we present a theory of discr ete funct ion space s using concepts from algebraic topol ogy. Cohomology theory and its topol ogical invar iance is empha sised. We will show how these concepts influence the choic e of discr ete space s for both finit e and boundary element metho ds. Space s on simpl icial manifolds (tria ngles, tetra hedra), carte sian product manifolds (quadrilaterals , hexahedra) and prismatic manifolds are constructed in the light of these topol ogical consi derations. We show that in parti cular, Nedel ec, Ravia rt-Thomas, Whitney and Rao-Wilton-Glis son type funct ion space s are easil y obtai ned as speci al cases .
Walker SP, Bluck MJ, Chatzis I, 2002, The stability of integral equation time-domain computations for three-dimensional scattering; similarities and differences between electrodynamic and elastodynamic computations, 4th International Workshop on Computational Electromagnetics in the Time Domain: TLM/FDTD and Related Techniques CEM TD, Publisher: JOHN WILEY & SONS LTD, Pages: 459-474, ISSN: 0894-3370
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- Citations: 25
Bluck MJ, Walker SP, Pocock MD, 2001, The extension of time-domain integral equation analysis to scattering from imperfectly conducting bodies, IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, Vol: 49, Pages: 875-879, ISSN: 0018-926X
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- Citations: 7
Ordovas R, Walker SP, Bluck MJ, 2000, Transient electromagnetic scattering from curved dielectric/lossy 3D bodies using covariant projection elements, 14th Annual Review of Progress in Applied Computational Electromagnetics (Monterey USA)
Bluck MJ, Walker SP, Thomas CM, 2000, Time domain modelling of a pulsed horn-dish antenna, 15th Annual Review of Progress in Applied Computational Electromagnetics (Monterey USA)
Ordovas R, Bluck MJ, Walker SP, 1999, Isoparametric curvilinear covariant projection elements for finite element time domain analysis of electromagnetic scattering, IEEE Transactions on Antennas and Propagation, ISSN: 0018-926X
Suchivoraphanpong V, Walker SP, Bluck MJ, 1999, Extending integral equation time domain acoustic scattering analysis to larger problems, International Journal for Numerical Methods in Engineering, Vol: 46, Pages: 1997-2010, ISSN: 0029-5981
Suchivoraphanpong V, Walker SP, Bluck MJ, 1999, Extending integral equation time domain acoustic scattering analysis to larger problems, International Journal for Numerical Methods in Engineering, Vol: 46, Pages: 1997-2010, ISSN: 0029-5981
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